This application relates to a process for treating acid whey, a by-product from the manufacture of cottage cheese or other fresh cheeses, and converting it into a valuable product while at the same time avoiding the customary high organics discharge into waste water treatment systems.
Cheese whey is reported to be the largest single by-product of the dairy industry. This whey is customarily discharged into municipal sewage systems which creates a most difficult disposal problem as most cheese plants are located in urban areas. It contains about half of the nutritive value of the milk from which the cheese is produced and, in the case of acid whey from cottage cheese manufacture, it contains levels of lactose sugar, protein, lactic acid and mineral salts. Cheese whey disposal is a difficult problem from the standpoint of pollution due to the organic nutrients contained therein and it has been estimated that as compared to domestic waste water, a quantity of one thousand gallons per day of raw whey discharged into a municipal sewage system can impose a load about equal to that generated by one thousand, eight hundred people.
While the solids of sweet whey are much more readily utilized as an animal or human food material than those of acid wheys, the acid wheys represent the major portion of the liquid wheys which are not being utilized. As an indication of the volume of acid wheys which are generated, acid wheys are produced in the making of cottage cheese, cream cheese, baker's cheese, neufchatel cheese, ricotta cheese and other fresh cheeses as distinguished from aged cheeses like cheddar cheese and swiss cheese.
The problem of whey disposal is substantial, particularly in view of the fact that many municipal treatment facilities which process the discharged whey are making substantial surcharges to the cheese processors. Indeed, concern exists as to the continued availability of municipal treatment facilities in many areas to accept and process discharged whey, notwithstanding the treatment charges and surcharges which are applied.
As will be apparent from the conditions outlined above, there exists a substantial need for a convenient, cost-effective process or procedure for the processing of whey discharge fluids. The dairy industry has considered various approaches for the treatment of cheese wheys, especially acid wheys, and a review of some of these proposals is given in Wix and Woodbine, Dairy Sci. Absts. 18:537-548 and 621-630. Various procedures have been described in the patent literature as well, including converting whey solids to an edible yeast cell mass in which the protein and carbohydrate content of cheese whey is converted substantially entirely to yeast cells as described in U.S. Pat. No. 3,818,109 and various publications mentioned therein. Fermentative utilization of whey has been proposed which, in theory, provides a means for increasing the nutritive value of the whey as compared to dried whey products, and yeasts in particular have been considered as fermentative agents. However, such procedures have not reached a point of practical application.
Prior to the present invention, insofar as we are aware there has not been developed a commercially practical method for the treatment of acid whey, substantially eliminating the organic waste loads which it represents, and essentially converting the acid whey into a commercially useful yeast product. Where the objective is to produce a synthetic bread flavor, it has been proposed that pasteurized whey substrates of 6 to 40% solids can be fermented with a yeast, such as Saccharomyces cerevisiae (Baker's yeast), and a coccus bacteria, such as an enterococcus of serological group D, to produce lactic acid in situ. This is necessary since Baker's yeast is capable of utilizing lactic acid but not lactose. Instead of the bacteria, lactic acid can be added directly. The medium is aerated during fermentation for a growth period of up to 24 hours. A nitrogen source, such as diammonium phosphate, may be added to the whey medium. (See Bundus, et al U.S. Pat. Nos. 3,466,174 and 3,466,176). In the Bundus, et al. process, only part of the whey proteins and lactose are utilized, and the process is terminated with the substrate containing about 5% by volume of yeast together with whey protein and lactose thus not substantially eliminating the organics content of the discharged product as is the object of the present invention. Preferably, as described in U.S. Pat. No. 3,466,176, the whey protein is subjected to a high heat treatment before being utilized in the process, which is said to enhance the development of the desired bread flavor. Apparently, this is due to partial heat denaturation of the whey protein which inhibits some of the utilization of the protein by the growing yeast.
The process of the present invention is distinguished from the Bundus et al type of process in such features as the whey treatment procedures, sugars hydrolysis, fermentation and nature of the product produced, among others.